JPH11315775A - Ionic current detection device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the influence of power source fluctuation noises from ionic current signals. SOLUTION: When ionic current is detected by an ionic current detection circuit 24, the fluctuation of battery voltage VB is detected by a power source fluctuation noise cancel signal generation circuit 31, and a noise cancel signal Vd is generated. This noise cancel signal Vd becomes a phase and reverse phase signal of power source fluctuation noises which is superimposed on the ionic current signal via an ignition coil 11 from the battery side. By imprinting this noise cancel signal Vd on the ionic current signal which is output from the ionic current detection circuit 24, the power source fluctuation noises superimposed on the ionic current signal is canceled. As a result, the ionic current signal which is input to a band pass filter 25 becomes a clear ionic current in which the power source fluctuation noises are eliminated and a knocking signal which is uninfluenced by power source fluctuation noises is output from the band pass filter 25 so that misjudgment of knocking due to power source fluctuation noise is prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ion current detector having a function of removing power supply fluctuation noise superimposed on an ion current signal detected through a spark plug.

[0002]

2. Description of the Related Art In recent years, in order to detect a combustion state of an internal combustion engine, an ion current flowing through a terminal of a spark plug is detected for each ignition, as shown in Japanese Patent Application Laid-Open No. 6-299941.
Techniques for detecting misfire, knocking, and the like based on the ion current signal have been developed. Conventionally, it has been known that LC resonance noise due to residual magnetic energy of an ignition coil occurs immediately after spark discharge as noise superimposed on an ion current signal.
In Japanese Patent No. 41, the ion current signal is invalidated (masked) for a predetermined period after the end of the spark discharge, so that the LC resonance noise immediately after the spark discharge is removed.

When knocking is detected from an ionic current signal, a signal component in a knocking occurrence frequency band from the ionic current signal is used to reduce the influence of noise, as disclosed in Japanese Patent Application Laid-Open No. 61-57830. In some cases, the presence or absence of knocking is determined by separating signal components in other frequency bands.

[0004]

Incidentally, an ion current detection circuit for detecting an ion current through a spark plug includes:
Since it is connected to the secondary side of the ignition coil, the voltage fluctuation of the power supply (battery) that supplies current to the primary coil of the ignition coil is transmitted to the secondary side through the ignition coil, and it is generated as power supply fluctuation noise. Superimposed on the ion current signal.
Since the influence of the power supply fluctuation noise appears after the LC resonance noise immediately after the spark discharge is attenuated as shown in FIG. 4B, the influence of the power supply fluctuation noise immediately after the spark discharge as in the former (Japanese Patent Laid-Open No. 6-299941). The exclusion of the LC resonance noise alone cannot completely eliminate the influence of the power supply fluctuation noise, and may cause erroneous determination of knocking or the like.

In addition, since power supply fluctuation noise sometimes includes a component in a knocking occurrence frequency band, as in the latter case (JP-A-61-57830), a signal in a knocking occurrence frequency band is converted from an ion current signal. Even if the component is extracted, there is a possibility that power fluctuation noise is included in the signal component, and there is also a possibility that knocking or the like is erroneously determined.

SUMMARY OF THE INVENTION The present invention has been made in view of such circumstances, and accordingly, an object of the present invention is to reduce the influence of power supply fluctuation noise from an ion current signal and improve the accuracy of ion current detection. It is an object of the present invention to provide an ion current detection device capable of performing the above-described operations.

[0007]

According to a first aspect of the present invention, there is provided an ion current detecting apparatus for detecting an ion current from a power supply via an ignition coil when an ion current is detected by the ion current detecting means. The power fluctuation noise canceling means generates a signal having a phase opposite to the power fluctuation noise to be superimposed on the signal, and applies the signal having the opposite phase to the ion current signal. In this way, the power supply fluctuation noise superimposed on the ion current signal and the signal of the opposite phase cancel each other, and the power supply fluctuation noise in the ion current signal is reduced. This makes it possible to detect an ion current which is less affected by power supply fluctuation noise, improve the detection accuracy of the ion current, and accurately determine the combustion state of the internal combustion engine from the ion current signal.

In this case, it is preferable to detect the voltage fluctuation of the power supply which is the source of the power supply fluctuation noise and invert the waveform of the voltage fluctuation to generate the signal having the opposite phase. As described above, if the voltage fluctuation of the power supply which is the source of the power supply fluctuation noise is detected and the signal of the opposite phase is generated, the signal of the opposite phase corresponding to the power supply fluctuation noise can be generated with high accuracy.

The power supply fluctuation noise superimposed on the ion current signal from the power supply side is transmitted through the primary-secondary capacitance of the ignition coil as shown in FIG. Delay. In consideration of this point, it is preferable to delay the phase of the signal having the opposite phase in accordance with the delay of the power supply fluctuation noise. By doing so, the phase of the signal having the opposite phase can be made to exactly match the phase of the power supply fluctuation noise, and the effect of canceling the power supply fluctuation noise by the signal having the opposite phase can be enhanced.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. First, a circuit configuration of an ignition control system and an ion current detection system will be described with reference to FIG. One end of a primary coil 12 of the ignition coil 11 is connected to a power supply terminal (+ B) to which a battery voltage VB is supplied, and the other end of the primary coil 12 is connected to a power transistor 1 for ignition control.
5 collectors. One end of a secondary coil 16 of the ignition coil 11 is connected to a spark plug 17, and the other end of the secondary coil 16 is connected to two Zener diodes 18,
19 is connected to the ground.

The two Zener diodes 18 and 19 are connected in series in opposite directions, a capacitor 20 is connected in parallel to one Zener diode 18, and an ion current detecting resistor 21 is connected in parallel to the other Zener diode 19. I have. Capacitor 20 and ion current detection resistor 2
1 is input to the negative input terminal of the amplifier circuit 23 via the resistor 22 and amplified. The ion current detection circuit 24 (ion current detection means) includes the zener diodes 18 and 19, the capacitor 20, the ion current detection resistor 2
1, an amplifier circuit 23 and the like. Output voltage of the ion current detection circuit 24 (output voltage of the amplification circuit 23)
Is a bandpass filter (BPF) as an ion current signal
25.

During the operation of the engine, the power transistor 15 is turned on / off by the rise / fall of the ignition signal IGt output from the microcomputer 28 for controlling the engine. When the power transistor 15 is turned on,
When a primary current flows from the battery (not shown) to the primary coil 12 and then the power transistor 15 is turned off,
When the primary current of the primary coil 12 is cut off, the secondary coil 1
6, a high voltage is electromagnetically induced, and a spark discharge is generated between the electrodes 30 and 29 of the spark plug 17 by the high voltage.

At this time, the spark discharge current flows from the ground electrode 29 of the spark plug 17 to the center electrode 30 and the secondary coil 16
, And flows to the ground side via the Zener diodes 18 and 19. After the capacitor 20 is charged, the ion current detection circuit 24 is driven using the charging voltage of the capacitor 20 regulated by the Zener voltage of the Zener diode 18 as a power source, and an ion current is detected as follows.

After the end of the spark discharge, a voltage is applied between the electrodes 30 and 29 of the spark plug 17 by the charging voltage of the capacitor 20, and ions generated when the air-fuel mixture burns are converted into ion currents as ion currents. , 29. This ion current is transmitted from the center electrode 30 to the ground electrode 2.
9 and then from the ground side to the ion current detecting resistor 2
1 to the capacitor 20.

At this time, the input potential Vin of the amplifier circuit 23 is changed according to the change of the ion current flowing through the ion current detecting resistor 21.
And an ion current signal of a voltage corresponding to the ion current is output from the output terminal of the amplifier circuit 23 to the band-pass filter 2.
5 is output. The filtering period of the band-pass filter 25 is controlled by a mask signal output from the microcomputer 27 in order to remove the LC resonance noise immediately after the spark discharge. As shown in FIG. Mask signal is low level L
During the ow period, a knocking signal in the knocking occurrence frequency band (for example, around 6 KHz) is extracted from the ion current signal and input to the peak hold circuit 26.

The peak hold circuit 26 starts the peak hold of the output signal of the band pass filter 25 at the same time as the filtering of the band pass filter 25 starts. The peak value of the knocking signal held by the peak hold circuit 26 is read into an engine control microcomputer 28 via an A / D converter 27.
The microcomputer 28 smoothes the peak value of the read knocking signal, and determines the presence or absence of knocking based on whether the smoothed value exceeds a knocking determination value.

By the way, when the primary current of the ignition coil 11 is cut off, as shown in FIG. 5, the fluctuation of the battery voltage VB is transmitted to the secondary side through the primary-secondary capacity C12 of the ignition coil 11, so that The secondary voltage V2 is the battery voltage VB
Will fluctuate. Due to the fluctuation of the secondary voltage V2, the secondary-side distributed capacitance C2 is charged and discharged, and the charging and discharging current flows to the secondary side as a power supply fluctuation noise current. Therefore, power supply fluctuation noise is superimposed on the ion current signal flowing to the ion current detection circuit 24 connected to the secondary side.

Therefore, in this embodiment, the power supply fluctuation noise canceling signal generation circuit 31 (power supply fluctuation noise canceling means) for canceling the power supply fluctuation noise superimposed on the ion current signal includes a power supply terminal (+ B) and the ion current detection circuit 24. Connected to the output terminal of Hereinafter, the configuration of the power supply fluctuation noise cancellation signal generation circuit 31 will be described with reference to FIGS.

The input circuit 32 of the power fluctuation noise canceling signal generating circuit 31 is configured by connecting two resistors 33 and 34 in series between a power supply terminal (+ B) and a ground terminal GND, and a battery voltage VB To two resistors 3
Voltage Va (resistors 33, 34) divided by a resistance ratio of 3, 34
Is the input voltage [see FIG. 3 (a)]. The intermediate connection point between the resistors 33 and 34 has an input voltage Va
A capacitor 35 for extracting the AC component (voltage fluctuation) is connected, and the fluctuation of the battery voltage VB is detected by the output voltage Vb of the capacitor 35 (see FIG. 3B).

On the other hand, a phase inversion circuit 37 using an operational amplifier 36 is provided at the output stage of the power supply fluctuation noise cancellation signal generation circuit 31. The output voltage Vb of the capacitor 35 (variation of the battery voltage VB) is input to the + input terminal of the operational amplifier 36 via the capacitor 38.
The output voltage Vb of the capacitor 35 (the variation of the battery voltage VB) is input to the input terminal via the resistor 39. Thus, the phase inverting circuit 37 shapes the output voltage Vb of the capacitor 35 into a waveform from which minute noise superimposed thereon has been removed, as shown in FIG. 3C, and superimposes the waveform on the ion current signal. After the voltage is attenuated to the same voltage as the power fluctuation noise, the voltage waveform is inverted as shown in FIG. 3D to generate a noise cancel signal Vd having a phase opposite to that of the power fluctuation noise. At this time, the operational amplifier 36
Also has a function (phase correction function) of delaying the phase of the noise cancellation signal Vd in accordance with the delay of power supply fluctuation noise superimposed on the ion current signal from the battery side. As a result, the noise cancellation signal Vd has the opposite phase to the phase of the power supply fluctuation noise superimposed on the ion current signal and has the same voltage as the power supply fluctuation noise.

The noise cancellation signal Vd output from the operational amplifier 36 is applied to the ion current signal output from the ion current detection circuit 24, whereby power supply fluctuation noise superimposed on the ion current signal is canceled by the noise cancellation signal Vd. (Cancelled).
As a result, as shown in FIG. 4A, the ion current signal input to the band-pass filter 25 becomes a net ion current from which power supply fluctuation noise has been eliminated. A knocking signal that is not received is output. Therefore, erroneous determination of knocking due to power supply fluctuation noise is prevented, and the accuracy and reliability of knocking determination are improved.

In the above-described embodiment, the present invention is applied to a system for judging the presence or absence of knocking from an ion current signal. However, a system for detecting another combustion state such as misfire or preignition from an ion current signal. The present invention is also applicable to the present invention.

In the above embodiment, the noise cancellation signal is applied to the output signal of the ion current detection circuit 24. However, the input signal of the ion current detection circuit 24 or the ion current transmitted through the ion current detection circuit 24 A power cancellation noise may be canceled by applying a noise cancellation signal to the signal.

In the above embodiment, the phase of the noise cancellation signal Vd is shifted in accordance with the phase of the power supply fluctuation noise superimposed on the ion current signal. However, the noise generated by detecting the fluctuation of the battery voltage VB The phase of the ion current signal (power supply fluctuation noise) may be shifted in accordance with the cancel signal Vd. The point is that the power supply fluctuation noise superimposed on the ion current signal and the noise cancellation signal have opposite phases. Just do it.

In addition, according to the present invention, the configuration of the power supply fluctuation noise canceling signal generation circuit 31 may be appropriately changed.
Various changes can be made without departing from the scope of the invention.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an ignition control system and an ion current detection system according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing a configuration of a power supply fluctuation noise cancellation signal generation circuit.

FIGS. 3A to 3D are diagrams showing signal waveforms at various parts of a power supply fluctuation noise canceling signal generation circuit.

FIG. 4A is a time chart showing a relationship between a mask signal, an ion current signal, and a knocking signal in the present embodiment, and FIG. 4B is a time chart showing a relationship between a mask signal, an ion current signal, and a knocking signal in a conventional system.

FIG. 5 is a circuit diagram for explaining the cause of generation of power supply fluctuation noise.

[Explanation of symbols]

11 Ignition coil, 17 Ignition plug, 21 Ion current detection resistor, 24 Ion current detection circuit (ion current detection means), 25 Bandpass filter, 26 Peak hold circuit, 28 Microcomputer, 31 Power supply Fluctuating noise canceling signal generation circuit (power supply fluctuating noise canceling means);

 ──────────────────────────────────────────────────の Continued on front page (72) Inventor Kazuhisa Mogi 1 Toyota Town, Toyota City, Aichi Prefecture Inside Toyota Motor Corporation

Claims (3)

[Claims] An electric current flowing from a power supply to a primary side of an ignition coil is interrupted by a switching means at each ignition timing.
An ignition device for inducing a high voltage on the secondary side of the ignition coil and applying the high voltage to a spark plug to generate a spark discharge, wherein an ion current generated during combustion of the air-fuel mixture is detected through the ignition plug. Current detection means; and power supply fluctuation noise for applying a signal having a phase opposite to that of power supply fluctuation noise superimposed on the ion current signal from the power supply side via the ignition coil to the ion current signal when the ion current detection means detects the ion current. An ion current detection device comprising: a cancel unit. 2. The power supply fluctuation noise canceling means,
2. The ion current detection device according to claim 1, further comprising: means for detecting a voltage fluctuation of the power supply; and means for inverting a waveform of the voltage fluctuation to generate the signal having the opposite phase. 3. The power supply fluctuation noise canceling means,
3. The ion current detection device according to claim 2, further comprising: means for delaying the phase of the signal having the opposite phase in accordance with the delay of power supply fluctuation noise superimposed on the ion current signal.